The present invention relates to a method and apparatus for handling after reeling, machine-width parent rolls reeled onto a reeling core, which come from a paper or board machine or are manufactured on a separate finishing line.
A parent reel refers to a machine-width reel manufactured on a paper machine or a board machine, which is wrapped around a reeling core, i.e. a parent reel iron. Parent reels are used to take manufactured paper or board to an intermediate store, prior to the paper being taken to a winder or the next processing stage. Usually, parent reels are used with off-line machinery, between the finishing equipment and the paper machine, and before the winder after finishing. As larger paper machines are nearly 10 m wide, parent reels are extremely heavy and require massive devices to move them. Parent reel diameters are about 3.5–4 m, so that wide parent reels weigh 120–160 t. The parent reels must sometimes be moved over long distances between the various production devices and store locations. Parent reel carts and quite often gantry cranes are used to move parent reels.
One problem associated with moving parent reels is taking them from the cart to the store and transferring them to the cart. This transfer generally takes place using rails tilted at 0.3–0.4°, along which the reels roll. The parent reels rest on such rails at the storage locations. Because the parent reels are very heavy and wide, this form of transfer causes many difficulties. The wide reels easily turn sideways as they roll. This can easily lead to their bearings dropping from the storage rails, which can damage the parent reel and the parent reel iron, while using a gantry, crane to lift the parent reel back onto the rails is both difficult and interrupts other reel handling. When parent reels are rolled along sloping rails from the parent reel cart to the storage irons or vice versa, a difference in height may occur between the ends of the rolling surfaces, allowing the heavy parent reel to drop onto the lower surface at these ends. This stepping wears the rails and the bearings of the parent reel and leads to their early replacement. When parent reels are moved by rolling, their movement onto and off the cart is difficult to control in other ways too. The speed of movement always depends on the slope used and cannot be altered. At the same time the parent reels can only be stopped at set stations, which have stops to arrest the movement.
To avoid the drawbacks referred to above, parent rolls can be moved using active transfer devices. In one such solution, double transfer cradles are arranged in connection with the storage irons. In this system, there is a double transfer cradle on the side of both storage rails, the transfer cradle having two transfer forks to be attached to the parent reels. Thus, a single transfer cart can be used to handle two parent reels. The transfer cradles are moved by means of a rack and pinion drive, the cradle drives being synchronized to prevent the parent reels from turning at an angle. The parent reel cart in turn has similar double transfer cradles, which are arranged to move in such a way that the parent reel is always received by the nearest transfer fork and correspondingly removed from the exit side using the nearest transfer fork. This makes the transfer cradle sufficiently long for it to be able to support the parent reel while it is moving from the side of the free end of the transfer cradle while the path of the cradle is made to extend from the parent reel cart to the reception point. In this solution, parent reels can be moved in a controlled manner, but at a storage station, for instance, the parent reel must be transferred from the transfer cradle of the parent reel cart to the cradles of the storage station, so that the transfer of the parent reel is considerably slower. If sloping rails are used to transfer the parent reel at the storage station, the system will have the weaknesses referred to above. Another significant drawback of this solution is that mechanically highly complicated and expensive devices are required both in the cart and at the storage location. In particular, the racks required by the transfer cradles and suitable rack and pinion drives for them increase costs, as does the synchronization of the parallel drives. Though the double-cradle solution of the parent reel cart permits an extremely strong construction, this same construction also becomes extremely heavy. As the transfer cradles are permanently attached to the cart, their paths are limited and the cart's cradles can only be used to transfer parent reels to and from the cart, but not, for example, to transfer the parent reels to a desired location at the storage station. The fact that separate transfer devices are required at both the receiving station and in the parent reel cart also contributes to the high cost of the solution.